TAMPA — The Hillsborough County school district this week submitted student records and other information requested as part of a federal investigation into single-sex programs in district schools that was launched after the American Civil Liberties Union lodged a complaint.

The ACLU filed a complaint in May with the U.S. Department of Education’s Office of Civil Rights. In the complaint, the group says the district has spent hundreds of thousands of dollars in taxpayer money to enact a “hidden curriculum” based on the idea that boys and girls need to be taught differently.

In an example, the ACLU says teachers in all-boys classes are encouraged to “be louder” and that teachers in all-girls classes are expected to be calmer and less critical.

In a letter sent Monday that accompanied the requested information, school district attorney Tom Gonzalez wrote that to be an official complaint, the complainant has to be someone who claims to be directly discriminated against, which isn’t the case with the ACLU.

“That investigation should not, and cannot, be conducted in circumstances in which a party having no standing except its opposition to all single-sex education seeks to renew a debate that has been settled,” Gonzalez wrote.

School district spokesman Stephen Hegarty said Hillsborough’s single-gender programs and schools are voluntary; parents can choose to enroll their children there but aren’t forced to.

Last school year, about 2,000 of the district’s 200,000-plus students were educated in one of two single-gender schools or in a single-gender classroom in 10 other schools.

In 2011, Hillsborough opened two single-gender middle magnet schools in East Tampa. Franklin Middle Magnet School became Franklin Boys Preparatory Academy, and Ferrell Middle Magnet became Ferrell Girls Preparatory Academy. Both schools previously struggled with academics, but they were given an A rating by the Florida Department of Education for the 2013-14 school year.